Simple script for posting a valid response back to Paypal service after a sale is completed using the Paypal Instant Checkout payment method. <?php // read the post from PayPal system and add 'cmd' $req = 'cmd=_notify-validate'; foreach ($_POST as $k...

If you use the Paypal sandbox you'll notice that there is an IPN Simulator test tool. You must be logged to use it. This tool lets you test an IPN handler script for your application. If your script is not correct and you try to send a test IPN transactio...